The present invention is directed, in general, to polishing pad alignment device and method and, more specifically, to a polishing pad alignment device for semiconductor wafer polishing pads and method of use for the chemical mechanical planarization of semiconductor wafers.
Chemical/mechanical polishing (CMP) is an essential process in the manufacture of semiconductor chips today and is becoming more critical as device sizes continue to shrink into the lower submicron ranges. Because of the high capital expense in a clean room and the high cost of manufacture, chip failures due to manufacturing defects and system down time must be minimized. Combined with seemingly, ever-falling chip prices, quality control during all phases of chip manufacture is of the highest priority.
The conventional CMP process has been developed for providing smooth topographies of the semiconductor wafers for subsequent lithography and material deposition. The CMP process can be used for planarizing: (a) insulator surfaces, such as silicon oxide or silicon nitride, deposited by chemical vapor deposition; (b) insulating layers, such as glasses deposited by spin-on and reflow deposition means, over semiconductor devices; or (c) metallic conductor interconnection wiring layers. Semiconductor wafers may also be planarized to: control layer thickness, sharpen the edge of via xe2x80x9cplugsxe2x80x9d, remove a hardmask, remove other material layers, etc. Typically, a given semiconductor wafer may be planarized several times, such as upon completion of each metal layer.
Referring now to FIG. 1, illustrated is a sectional view of a conventional semiconductor wafer polishing apparatus 100 comprising a drive shaft 160, a platen 170, a polishing pad 172, a conventional semiconductor wafer 190, a wafer backing pad 120, and a carrier head 110. One who is skilled in the art is familiar with the operation of the conventional semiconductor wafer polishing apparatus 100.
As is well known, the CMP process involves holding and rotating a thin, reasonably flat, semiconductor wafer 190 against a rotating, polishing surface. The polishing surface is conventionally a polyurethane pad (polishing pad 172) affixed to the platen 170. During the CMP process, the polishing pad 172 becomes clogged with slurry and polishing by-products. Typically, the polishing pad 172 is re-conditioned several times before being discarded. However, the polishing pad 172 must be replaced after a predetermined significant number of wafers have been planarized due to wear and deterioration. Second, the polishing pad 172 must be replaced whenever a wafer 190 breaks, as a broken wafer contaminates the polishing environment with silicon. Of course, the removal and replacement process of the misaligned polishing pad 172 is very time consuming, resulting in down time for the CMP apparatus and significant labor costs and lost production.
In conventional processes, when replacing the polishing pad 172, the operator must align the outer circumference of the polishing pad 172 with the platen 170 in order that the polishing pad 172 is centered on the platen 170. Depending on the operator""s dexterity and size, this may be time consuming. Also, after the operator aligns the pad, the operator has to hold the polishing pad 172 down while, at the same time, peeling the plastic backing off the polishing pad 172 in order to expose the adhesive and paste the polishing pad 172 onto the platen 170. During this operation, the polishing pad 172 may slip out of alignment several times. Consequently, the operator may have to repeatedly realign the polishing pad 172 with the platen 170 before the polishing pad 172 is successfully stuck onto the platen 170.
Additionally, because adhering the polishing pad 172 onto the platen 170 is done manually, alignment of the polishing pad 172 may vary as a function of human error. As consistency of the polishing environment is a high priority to maintain extremely precise CMP processes from wafer to wafer, this variation is undesirable. Moreover, if the polishing pad 172 is inadvertently misaligned and stuck to the platen 170, it must then be moved, which not only destroys the polishing pad 172 but also increases down time and cost in materials.
Accordingly, what is needed in the art is an apparatus and method that remedies the deficiencies associated with these conventional methods.
To address the above-discussed deficiencies of the prior art, the present invention provides a polishing pad alignment device having an alignment member positionable against a side wall of a platen. The height of the alignment member is sufficient to extend above a top surface of the platen when positioned against the wall of the platen. In one embodiment, the alignment member is an arcuate member having an arc substantially equal to an arc of the platen. In another embodiment, the alignment member is removably attachable to the wall of the platen, and the polishing pad alignment member further includes an attachment device configured to attach the alignment member to the platen. In one aspect of this embodiment, the attachment device is a pin coupled to a wall of the polishing pad alignment member, the pin being configured to be cooperatively received in a corresponding pin receptacle in the wall of the platen when the polishing pad alignment member is positioned against the wall of the platen. In another aspect of this embodiment, the polishing pad alignment device is metal and the attachment device is a magnet that magnetically retains the polishing pad alignment device against the wall of the platen. In yet another aspect of this embodiment, the attachment device is a latch that cooperatively engages a corresponding latch receptacle on the wall of the platen.
In another embodiment, the polishing pad alignment device includes a retractor device that couples the polishing pad alignment device to the platen. The retractor device includes a counter-balance weight attachable to the wall of the platen on an opposing side of the platen. In one aspect of this embodiment, the retractor device is a piston, a hinge, or a slide arm with a cooperative eyelet and retaining bolt.
The foregoing has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.